Sucrose synthase (SuSy), a key enzyme in sucrose metabolism, plays an important role in both plant growth and development and osmotic adjustment. A cDNA sequence of sucrose synthase gene, designated AhSuSy (GenBank accession number: JF346233), was isolated from peanut using homologous cloning, RACE, and TAIL-PCR. The full-length of AhSuSy cDNA is 2 790 bp, contained an ORF of 2 421 bp, the 5UTR and 3'UTR of 57 bp and 312 bp, respectively. A peptide of 806 amino acid residues was deduced according to the ORF, which showed more than 75% homologous to the corresponding proteins in soybean, Arabidopsis and maize. The AhSuSy was ligated into pET-32a(+) and transformed into E. Coli competent cell. After induced by IPTG, the fusion protein was obtained and its relative molecular weight was 92 kD, which was consistent with the theoretical value. The tissue specific expression analysis by using semi-quantitative RT-PCR assays indicated that AhSuSy was expressed in root, stem and leaf. After treated with 10% PEG, seedlings of peanut were used to determine transcript level for AhSuSy, sucrose synthase activity and sucrose content. The result showed that all of the three parameters were gradually increased during 4h to 12 h after treatment and the correlation coefficient between sucrose synthase activity and sucrose content was 0.993 (P=0.007<0.01) during this period, then declined from 12 h to 24 h after treatment, which indicated that AhSuSy may play a key role in adaptation of plants to drought stress.%蔗糖合酶(sucrose synthase,SuSy)是蔗糖代谢途径中的关键酶,在植物生长、发育和渗透调节过程中起着重要的作用.本研究利用同源克隆、RACE和TAIL-PCR相结合的方法从花生叶片中分离了蔗糖合酶基因,命名为AhSuSy (GenBank登录号为JF346233).该基因cDNA序列全长2 790 bp,包含一个2 421 bp的开放阅读框(ORF),5’端非编码区57 bp,3’端非编码区为312 bp.根据编码区预测AhSuSy编码806个氨基酸,与大豆、拟南芥、玉米等植物中相关蛋白的氨基酸序列同源性达75％以上；成功构建了该基因的原核表达载体pET32a-AhSuSy,在IPTG诱导下得到92 kD左右的蛋白,与理论值一致.半定量RT-PCR分析表明AhSuSy在花生根、茎、叶中均有表达.利用10％PEG模拟干旱处理花生幼苗,分析胁迫后AhSuSy的转录水平,同时测定蔗糖合酶活性和蔗糖含量,发现三者均表现为处理后4～12 h逐渐升高,相关性分析显示花生中蔗糖含量与蔗糖合酶活性的相关系数达0.993 (P=0.007＜0.01),处理后12～24 h逐渐降低.推测该基因响应干旱调控,在花生抗旱胁迫中可能起着一定的作用.
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